Bump confluent-kafka from 2.6.0 to 2.8.0

Bumps [confluent-kafka](https://github.com/confluentinc/confluent-kafka-python) from 2.6.0 to 2.8.0.
- [Release notes](https://github.com/confluentinc/confluent-kafka-python/releases)
- [Changelog](https://github.com/confluentinc/confluent-kafka-python/blob/master/CHANGELOG.md)
- [Commits](confluentinc/confluent-kafka-python@v2.6.0...v2.8.0)

---
updated-dependencies:
- dependency-name: confluent-kafka
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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Author: dependabot[bot]